SK400 series, the materials are the special alloy steel for making screw which are imported from Japan and Europe.Trough 1050℃ vacuum quenching and three times of 520℃ tempering, four hours one time. The hardness will be HRC50-52, good function of toughness, softening resistance in high temperature, common function of anti-wear and moderate function of anti corrosion. Alloy compsition: C:0.96, Cr:18.5,Mo:0.75,Si:1, W:1.2, V:0.9, Co:0.7

Good mirror finishing, fit for optics products, LGP, lens,white, PC, transparent PMMA, good function of anti corrosion.